1. Field of the Invention
The present invention relates to an improvement of a segment type digital display device using particularly liquid crystal and electrochromic.
2. Description of the Prior Art
At present, liquid crystal and electrochromic are used in digital display devices, but their response speed in display greatly changes, often affecting the discriminatability through sight.
More particularly, the response speed of liquid crystal is low at low temperatures, and a certain liquid crystal has a drawback such that its response at the time of OFF (extinguishing) is slow as compared with that at the time of ON (lighting). As a result, for example in a 7-segment type liquid crystal display device, when a numeric display " " is going to change into " ", there temporarily appears " " resulting from overlap of the numerals " " and " ". Besides, at low temperatures, such a transitional display continues to appear for a relatively long time, thus causing deterioration of discriminatability and a misunderstanding.
In general, when a segment has changed from OFF state to ON state, if viewed in a certain time range only, there is the tendency that the longer the OFF state just before ON, the greater the response delay. According in case plural segments turned ON from OFF, they do not become discriminatable at a same time but become discriminatable at random, and the display of a meaningless pattern results. Thus, the deterioration of discriminatability is so much accelerated.
In conventional display devices, in an effort to eliminate such drawbacks, a heater is provided and is operated when the temperature falls below a predetermined level to maintain the temperature of the display devices at above the predetermined level. In this case, however, the heater and its controlling unit are needed, to the display devices using them become large in size and require a large electric power for operating the heater, thus resulting in increased cost. In addition, pre-heating is required for obtaining an exact display. Thus, the service characteristics of those display devices have been poor.